Detection of radar targets at short range requires high range accuracy. The rms error in the range measurement is δR=c/(2βeff(2E/N0)0.5, where c is the speed of light, βeff is the effective bandwidth of the radar signal, E is the signal energy, and N0 is the noise power per unit bandwidth. The transmitted radar signal must therefore be wideband or high power to achieve high range accuracy. Three primary radar architectures are available for short range detection: linear frequency modulated (FM) pulse compression radar, frequency modulated continuous wave (FM-CW) radar, and short-pulse Doppler radar. In general, transmitters for pulse compression radar require more source components than FM-CW or the short-pulse Doppler implementations.
For each of the aforementioned architectures, the required peak transmit power increases as the length of the transmitted pulse decreases, in order to attain a constant average power. However, for short range requirements and wide bandwidths, the required peak transmit power is less than 1 W, even for a short-pulse system. The pulsed systems provide high levels of transmitter-to-receiver isolation because the transmitter and receiver do not operate simultaneously. On the other hand, the transmitter and receiver in a CW system are always on, leading to spillover, which must typically be mitigated.
Continuous wave radars theoretically do not have a minimum range, because both the transmitter and receiver operate continuously. Pulsed systems do have a minimum detectable range, because the receiver is not on when the transmitter is transmitting (i.e. to blind zones exist). As such, the minimum range of a pulsed system depends on the transmitted pulse width. This minimum range is shorter with short-pulse Doppler radar than with pulse compression radar.
The present work focuses on providing a wideband implementation of a coherent short-pulse radar transmitter that supports detection of targets at short range over a wide range of velocities.